1. Field of Endeavor
The present invention relates to endovascular therapies and shape memory polymer foams for endovascular therapies and more particularly to a shape memory polymer stent.
2. State of Technology
United States Patent Application 2003/0144695 by James, F. McGuckin and Richard T. Briganti, published Jul. 31, 2003, and United States Patent Application 2003/0009180 by Peter W. J. Hinchliffe, James, F. McGuckin, Richard T. Briganti, and Walter H. Peters, published Jan. 9, 2003, for a vascular hole closure device provides the following state of the technology information, “During certain types of vascular surgery, catheters are inserted through an incision in the skin and underlying tissue to access the femoral artery in the patient's leg. The catheter is then inserted through the access opening made in the wall of the femoral artery and guided through the artery to the desired site to perform surgical procedures such as angioplasty or plaque removal. After the surgical procedure is completed and the catheter is removed from the patient, the access hole must be closed. This is quite difficult not only because of the high blood flow from the artery, but also because there are many layers of tissue that must be penetrated to reach the femoral artery.”
United States Patent Application 2002/0133193 published Sep. 19, 2002, and U.S. Pat. No. 6,391,048 issued May 21, 2002, to Richard S. Ginn and W. Martin Belef, for an integrated vascular device with puncture site closure component and sealant and methods of use provides the following state of the technology information, “Catheterization and interventional procedures, such as angioplasty and stenting, generally are performed by inserting a hollow needle through a patient's skin and muscle tissue into the vascular system. A guide wire then is passed through the needle lumen into the patient's blood vessel. The needle is removed and an introducer sheath is advanced over the guide wire into the vessel. A catheter typically is passed through the lumen of the introducer sheath and advanced over the guide wire into position for a medical procedure. The introducer sheath therefore facilitates insertion of various devices into the vessel while minimizing trauma to the vessel wall and minimizing blood loss during a procedure. Upon completion of the medical procedure, the catheter and introducer sheath are removed, leaving a puncture site in the vessel. Commonly, external pressure is applied until clotting and wound sealing occurs. However, this procedure is time consuming and expensive, requiring as much as an hour of a physician's or nurse's time, is uncomfortable for the patient, and requires that the patient be immobilized in the operating room, cathlab, or holding area. Furthermore, a risk of hematoma exists from bleeding prior to hemostasis.”
U.S. Pat. No. 6,174,322 issued Jan. 16, 2001 to Bernhard Schneidt for an Occlusion device for the closure of a physical anomaly such as a vascular aperture or an aperture in a septum provides the following state of the technology information, “The human circulatory system is comprised of a cardiovascular circulation and pulmonary circulation. In the embryonic phase of the development of a human being, the two circulatory systems are joined by the ductus arteriosus. The ductus connects the aorta (systemic circulation) with the pulmonary artery (pulmonary circulation). In the normal development of an infant, this ductus closes after birth. In pathological development, the ductus may not close so that the two circulatory systems remain connected even after birth. This can reduce the life expectancy of the infant. Closure of the ductus by means of a surgical procedure is well-known. However, this procedure is very cost-intensive and is connected with a risk for the patient. Closure of the ductus by means of an IVALON.®. (polyvinyl alcohol) foam plug (Porstmann method) is also well-known. In this case, a guide rail is introduced via a femoral vein into the aorta, through the ductus into the pulmonary artery and from there through the right ventricle and the right atrium and finally to the outside again via the opposite femoral vein. The ductus plug is then pushed into the ductus where it is ‘jammed in place.’ Owing to the high pressure differential) between the aorta and pulmonary artery, high demands are placed on the fixation of the ductus plug within the ductus.”
United States Published Patent Application No. 2005/0267570 by John H. Shadduck for endovascular occlusion devices and methods of use, published Dec. 1, 2005, provides the state of the technology information set out below.
The Published Patent Application No. 2005/0267570 “invention relates to an implant body that includes a shape-transformable polymeric structure for self-deployment within vasculature, and can be an open-cell shape memory polymer in the form of a microfabricated structure or a foam and also can be carried about a skeletal stent to provide stress-free means for occluding an AVM without applying additional pressures to the distended walls of an AVM.”
“Numerous vascular disorders, as well as non-vascular disorders, are treated by occluding blood flow through a region of the patient's vasculature. For example, aneurysms, fistulas, varicose veins and the like are treated with vessel occluding devices. Tumors and the like are also treated with endovascular embolic elements to terminate blood flow. Several procedures are described below.”
“An intracranial aneurysm is a localized distension or dilation of an artery due to a weakening of the vessel wall. In a typical example, a berry aneurysm is a small bulging, quasi-spherical distension of an artery that occurs in the cerebral vasculature. The distension of the vessel wall is referred to as an aneurysm sac, and may result from congenital defects or from preexisting conditions such as hypertensive vascular disease and atherosclerosis, or from head trauma. Up to 2% to 5% of the U.S. population is believed to harbor an intracranial aneurysm. It is has been reported that there are between 25,000 and 30,000 annual intracranial aneurysm ruptures in North America, with a resultant combined morbidity and mortality rate of about 50%. (See Weir B., Intracranial aneurysms and subarachnoid hemorrhage: an overview, in Wilkins R. H., Ed. Neurosurgery, New York: McGraw-Hill, Vol. 2, pp 1308-1329 (1985)).”
“Rupture of a cerebral aneurysm is dangerous and typically results in bleeding in the brain or in the area surrounding the brain, leading to an intracranial hematoma. Other conditions following rupture include hydrocephalus (excessive accumulation of cerebrospinal fluid) and vasospasm (spasm of the blood vessels).”
“Several methods of treating intracranial aneurysms are known including open surgeries and endovascular procedures. In an open craniotomy, a clip is placed at the base of the aneurysm. Long-term studies have established typical morbidity, mortality, and recurrence rates.”
“The least invasive approach for treating intracranial aneurysms is an endovascular method—which consists of a reconstructive procedure in which the parent vessel is preserved. Luessenhop developed the first catheter-based treatment of an intracranial aneurysm (see Luessenhop A. J., Velasquez A. C., Observations on the tolerance of intracranial arteries to catheterization, J. Neurosurg. 21:85-91 (1964)). At that time, technology was not yet developed for successful outcomes. Serbinenko and others deployed latex balloons in intracranial aneurysms (see Serbinenko, F. A., Balloon catheterization and occlusion of major cerebral vessels, J. Neurosurg. 41:125-145 (1974)) with mixed results.”
“More recently, Guglielmi and colleagues succeeded in developing microcatheter-based systems (GDC or Guglielmi detachable coil systems) that deliver very soft platinum microcoils into an aneurysm to mechanically occlude the aneurysm sac. After the position of the microcoil is believed to be stable within the aneurysm sac, the coil is detached from the guidewire by means of an electrolytic detachment mechanism and permanently deployed in the aneurysm. If coil placement is unstable, the coil can be withdrawn, re-positioned or changed-out to a coil having different dimensions. Several coils are often packed within an aneurysm sac. Various types of such embolic coils are disclosed in the following U.S. patents by Guglielmi and others: Nos. 5,122,136; 5,354,295; 5,843,118; 5,403,194; 5,964,797; 5,935,145; 5,976,162 and 6,001,092.”
“Microcatheter technology has developed to permit very precise intravascular navigation, with trackable, flexible, and pushable microcatheters that typically allow safe engagement of the lumen of the aneurysm. However, while the practice of implanting embolic coils has advanced technologically, there still are drawbacks in the use of GDC-type coils. One complication following embolic coil implantation is subsequent recanalization and thromobembolitic events. These conditions are somewhat related, and typically occur when the deployed coil(s) do not sufficiently mechanically occlude the volume of the aneurysm sac to cause complete occlusion. Recanalization, or renewed blood flow through the aneurysm sac, can cause expansion of the sac or migration of emboli from the aneurysm. Recanalization can occur after an implantation of a GDC coil if the coil does not form a sufficiently complete embolus in the targeted aneurysm. After the initial intervention, the body's response to the foreign material within the vasculature causes platelet activation etc., resulting in occlusive material to build up about the embolic coil. After an extended period of time, the build-up of occlusive material about the foreign body will cease. If spaces between the coils and occlusive material are too large, blood flow can course through these spaces thus recanalizing a portion of the thin wall sac. The blood flow also can carry emboli from the occlusive material downstream resulting in serious complications.”
“Alternative treatments include endovascular occlusion of the aneurysm with a liquid polymer that can polymerize and harden rapidly after being deployed to occlude the aneurysm. Wide neck aneurysms make it difficult to maintain embolic or occlusive materials within the aneurysmal sac—particularly liquid embolic materials. Such embolic materials can dislocate to the parent vessel and poses a high risk of occluding the parent vessel.”
“Another approach in the prior art is to provide an aneurysm liner of a woven or braided polymeric material such as polypropylene, polyester, urethane, teflon, etc. These mesh materials are difficult to use in treating larger aneurysms, since the materials cannot be compacted into a small diameter catheter.”
“Any method of endovascular occlusion with packing materials risks overfilling the sac and also the risk of agent migration into the parent vessel. Any overfill of the sac also will cause additional unwanted pressure within the aneurysm.”
“Another past method for occluding aneurysm sac used an elastic, expandable balloon member or liner that was introduced into the aneurysm and thereafter detached from the catheter. Such balloon implants are not likely to conform to the contours of an aneurysm and thus allow blood canalization about the balloon surface. A balloon also can cause undesired additional pressure on the aneurysm wall if oversized. The deployment and implantation of a balloon that carries stresses that may be released in uncontrollable directions is highly undesirable. Such balloon treatments have been largely abandoned.”
“Further, there are some aneurysm types that cannot be treated effectively with an endovascular approach. In such cases, the treatment options then may be limited to direct surgical intervention—which can be highly risky for medically compromised patients, and for patient that have difficult-to-access aneurysms (e.g., defects in the posterior circulation region).”
“The first type of intracranial aneurysm that cannot be treated effectively via an endovascular approach is a wide-neck aneurysm. In many aneurysms, the shape of the aneurysm sac is shape like a bowler's hat, for example, in which the neck/dome ratio is about 1:1. For the best chance of success in using an embolic coil, an intracranial aneurysm should have a narrow neck that allows the coils to be contained inside the aneurysmal sac. Such containment means that migration of the coil is less likely, and the possibility of thromboembolic events is reduced. To promote coil stability in wide-neck aneurysms, surgeons have attempted to temporarily reduce the size of the aneurysm neck by dilating a non-detachable balloon during coil deployment thereby allowing the coils to engage the walls of the sac while the neck is blocked. Another type of aneurysm that proves difficult to occlude with embolic coils is a fusiform aneurysm that bulges a large portion of the vessel lumen. Yet another type of aneurysm that responds poorly to endosaccular coiling is a giant aneurysm. In these cases, the recanalization rates remain high, the risk for thromboembolic phenomena is high, and the mass effect persists which related to the lack of volume reduction over time. The treatment of abdominal aortic aneurysms also would benefit from new implant systems that will better engage the vessel wall and occlude the distended vessel wall.”
“What is needed, in particular, are vaso-occlusive systems and techniques that are reliable and self-deploying for many types of vascular disorders, for example to occlude varicose veins. In particular, improved systems are needed for endovascular treatment of bifurcation aneurysms, wide-neck aneurysms, fusiform aneurysms and giant aneurysms that can provide acceptable outcomes.”
United States Published Patent Application No. 2005/0267570 by John H. Shadduck for endovascular occlusion devices and methods of use, published Dec. 1, 2005, is incorporated herein by this reference.